[sensors] [mac] Implement ambient light sensor for macOS

device/generic_sensor/platform_sensor.h

Index: device/generic_sensor/platform_sensor.h
diff --git a/device/generic_sensor/platform_sensor.h b/device/generic_sensor/platform_sensor.h
index 2019d343af4eb9410b82e75a36c84029f356725c..cfbb6afd253c77c43e7244baf93a8e081e77419d 100644
--- a/device/generic_sensor/platform_sensor.h
+++ b/device/generic_sensor/platform_sensor.h
@@ -65,6 +65,7 @@ class PlatformSensor : public base::RefCountedThreadSafe<PlatformSensor> {
   void NotifySensorError();
 
   mojo::ScopedSharedBufferMapping shared_buffer_mapping_;
+  PlatformSensorProvider* provider_;
 
  private:
   friend class base::RefCountedThreadSafe<PlatformSensor>;
@@ -72,7 +73,6 @@ class PlatformSensor : public base::RefCountedThreadSafe<PlatformSensor> {
   mojom::SensorType type_;
   base::ObserverList<Client, true> clients_;
   ConfigMap config_map_;
-  PlatformSensorProvider* provider_;
   base::WeakPtrFactory<PlatformSensor> weak_factory_;
   DISALLOW_COPY_AND_ASSIGN(PlatformSensor);
 };